Variable Switch

You're a computer programmer, and the program you're writing has numeric variables A and B. You need the computer to switch the variables so that the number in variable A becomes variable B, and the number in variable B becomes variable A. Adding a third variable would use more memory though, so how can you do that switch without using another variable? Use commands such as B=B-A to assign a new value to B.

Answer:

B = A+B
A = B-A
B = B-A

Using an example, if A=5 and B=4:
B = 5+4
A = 9-5
B = 9-4
A is now 4 and B is now 5.